Rapid process simulator



April 7, 1970 H. FRlcKE, JR., ET AL 3,505,512

RAPID PROCES S S IMULATOR 9 Sheets-Sheet l Filed Oct. 13, 1965 INVENTORS LOUIS H. FRICKE.JR. ROBERT A. WALSH ATTORNEY April 7, i970 H. FRICKE, JR., ET AL 3,505,512

RAPID PROCESS SIMULATOR 9 SheetS-Sheec 2 Filed Oct. 13, 1965 Emmllllll INVENTORS ATTORNEY Emma IN/ .vm

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KOP Umjmw, MUZ/xm April 7, 1970 H. FRICKE, JR., ET AL 3,505,512

RAPID PROCESS S IMULATOR 9 Sheets-Shea?l 5 Filed Oct. 13, 1965 lNVENTORS OUS H. FR|CKE,JR. ROBERT A. WALSH R OR R F E T DMF N E o OM C PA E \|?\..J D O I|||||IIML AT TORNEY April 7, 1970 I.. I-I. FRICKE, JR., ET AL 3,505,512

RAPID PROCESS SIMULATOR 9 Sheets-Sheet 4.

Filed Oct. 15, 1965 l I I I I I I I I I I I l I I I I I I I I I I I I I I I I I I I I I I I -b-- I I I I I' I I I I I I I I I I l I I IOO 26 if# 2B (JBO Lal

INVENTOR LOUIS H. FRICK JR. s

E, ROBERT A. wALsI-I FIG.3b.

ATTORNEY April 7, 1970 L. H. FRlcKE, JR., ET AL 3,505,512

` RAPID PROCESS SIMULATOR Filed Oct. 13, 1965 9 Sheets-Sheet 5 "'l n |73: 1 |75 AM'* i 66 i m g l i H z I l a n l s z |76 l i osclLLAroRY i TRANsu-:NTS GENERATOR |70 1 INVENTORS LOUIS H. FRICKE,JR. YROBERT A. WALSH ATTQRNEY April 7, 1970 L. H. FRICKE, JR., ET AL 3,505,512

RAPID PROCESS SIMULATOR Filed Oct. 13, 1965 l 9 Sheets-Sheet 6 AMPLITUDE DURATION O DELAY-2 1./

TRANSPORT DELAY i: :I/`DURATION F IG. 4

COM PU TE CYCL E INVENTORS LOUlS H. FRICKE, JR.

ROBERT A. WALSH BY O SIGN-AL T|ME ff/4,4% AMPLITUDE ATTORNEY April 7, 1970 Filed Oct. 13, 1965 l.. H. FRlcKE, JR., ET AL RAPID PROCESS SIMULATOR 9 Sheets-Sheet '7 ELECTRICAL 8. PNEUMATIC.

RAN G E SELECTOR PRO- CESS ERROW MODEl FlG.3e.

INVENTORS LOUIS F RICK JR. ROBERT A. WAL H ATTORNEY April 7, 1970 L.. H. FRICKE, JR., ET A1. 3,505,512

RAPID PROCESS S IMULATOR 9 Sheets-Sheet 8 DIGITAL VOLTMETER PROCESS Filed Oct. 13, 1965 .24eI 23e 247 INVENTORS LOUIS H. FRICKE, JR. ROBERT A. WALSH FIG.3P.

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ATTORNEY April 7, 1970 L.. H. FRICKE, JR., ET AL RAPID PROCESS SIMULATOR Filed Oct. l5, 1965 9 Sheets-Sheet 9 /32 3,0 FIG. 5

3II 309l 52 INPUT WAVE 2. PROCESS OUTPUT F IG. 6 a FIG. 6 b

0.4 2" MODEL OUTPUT ERROR SIGNAL FIG. 6 c FIG. 6 d

fEzdr 'O02 INvEN T'O Rs I OUIs H. PRICKEUR.

FIG. 6 e

ROBE RT A. WALSH ATTOR NEY U.S. Cl. 23S- 184 28 Claims ABSTRACT OF THE DISCLOSURE A rapid process simulator for determining both static and the dynamic characteristics which are unknownin a relatively stable process. The simulator includes a pulse generator for producing a perturbating pulse which is applied to the process. The perturbating pulse produces an output signal which can be expressed in the form of a polynomial. The process is compared in the simulator wth a model of orthogonal functions which are capable of being normalized to an orthonormal condition. The model is formulated with the idea of choosing a pulse input in such a way as to facilitate the construction of the system. An output signal is also produced in the model which is in turn compared with the output signal from the process in order to achieve an error signal. This signal is squared in the simulator and integrated to determine the characteristics of the system. The simulator includes a transport delay'device for delaying the perturbating pulse to the model with respect to the process, so that the output of the process and the model will begin in coincident times. In addition, the simulator is provided with a generator to produce oscillatory transients on a model of the signal to match transient on the process signal.

This invention relates in general to certain new and useful improvements in computer devices for determining process characteristics, and more particularly to la rapid process simulator which is capable of simulating process conditions, and comparing the process conditions against a known model of orthogonal functions.

In the design and development of controlled processes, there are two areas of intense activity. The rst of these areas lies in the theoretical simulation of the total plant and the second of these activities lies in the eflpirical simulations involving the collection of reilable experimental data to assist in the construction of a specialv purpose model. The simulation of a newly proposed process, even from the best available theoretical basis is usually only an approximate simulation. In most cases, it requires the employment of large and expensive computer installations, either analog and/or digital computers so that 'by direct programming of design criteria, the optimum plant operating conditions may be determined. These operating conditions may then be used to construct a pilot plant scale model. However, even if the model were reliable, the scale-up problems produced are quite complex. In many cases, it is almost impossible to maintain exact relationships between intrinsic parameters such as surface tension, heat transfer, etc. It is well established that few theoretical models, presently existing can anticipate all of the significant process characteristics. As a result of these complexities, many full scale plants are in need of partial redesign.

All of the presently available modes of analyzing operating processes involve disturbing the process and determining the reaction from the disturbance. The presently available methods generally employ a sinusoidal type of process change when attempting to obtain process characterization. However, delays between the input signal and the output of the process may take a number of days. In fact, complete tests often take months with the resultant upsetting of production. The newer method of disturbing a process is through the use of a controlled pulse. The pulse is generally selected so that some of its harmonies can produce a response of process output which yields all of the information that the sinusoidal techniques yield.

These pulse inputs and outp-uts can then be recorded and the data changed mathematically to Fourier transforms. The performance function, which is the ratio of output to input in this transform, is the measure of the frequency response of the entire system. This frequency response can, in turn, be depicted as a linear expression to show the relationship of input to output. This equation representing the performance function represents the model in an analog type of simulation. The procedure for fitting this linear model to a non-linear system is suiiicient to permit the devising of a correct control system within the normal range of operating conditions. However, Fourier analysis has the drawback of being difcult to perform in commercially operating plants and this fact makes a rapid description of the process diflicult to obtain, if not unavailable. Moreover, if the process is complex and difficult to describe, the techniques presently employed are not able to describe all of the existing process characteristics. It is generally necessary to acquire the data from the process, to prepare the data in a form for transformation by means of digital computer and then developing Fourier transforms for the various signals to determine the harmonic values of the different frequencies. In general, it is often very difficult to give a precise physical interpretation of the various parameters affecting the process from measurements in the field, when the process characteristics must be determined by use of both analog and digital computer techniques.

It is, therefore, the primary object of the present invention to provide a rapid process simulator for providing a determination of the dynamic characteristics of an actual process.

lt is another object of the present invention to provide a rapid process simulator of the type stated which is capable of determining both static and dynamic characte'ristics of a process by comparing process conditions to an established model and measuring the deviation therefrom. l

It is a further object of the present invention to provide' a rapid process simulator of the type stated which is capable of deriving simple linear models for characterizing a controllable process.

It is also an object of the present invention to provide a method of determining an analytical description and characterization of an existing process.

It is another salient object of the present invention to provide a rapid process simulator of the type stated which is portable in nature and capable of being transported to various locations for employment in a multitude of operating conditions.

With the above and other objects in View, our invention resides in the novel features of form, construction, arrangement and combination of parts presently described and pointed out in the claims.

In the accompanying drawings (9 sheets) FIGURE l is a front plan view of a rapid process simulator constructed in accordance with and embodying the present invention and showing in detail the control panel thereof;

FIGURE 2 is a schematic block diagram functionally showing the operative connection of the various component systems forming part of the rapid process simula-7 tor;

FIGURES 3a, 3b, 3c, 3d, 3e and 3f are a combined schematic wiring diagram showing in detail the component systems forming part of the rapid process simulator, of which;

FIGURE 3a schematically illustrates a triangular wave generator,

FIGURE 3b schematically illustrates a pulse generator,

FIGURES 3c and 3d schematically illustrate a model of orthogonal functions,

FIGURE 3c schematically illustrates an oscillatory transient generator,

FIGURE 3e schematically illustrates an electrical and pneumatic range selector,

FIGURE 3f schematically illustrates a summer, squarer, integrator, digital voltmeter and transducers;

FIGURE 4 schematically illustrates the waveforms of the pulses produced by the triangular wave generator and pulse circuits with respect to time; t

FIGURE 5 is a schematic wiring diagram showing an operative connection of the rapid process simulator to an unknown process; and

FIGURES 6a, 6b, 6c, 6d, and 6e illustrate the various waveforms produced in simulating the process of FIG- URE 5, wherein:

FIGURE 6a represents the input waveform,

FIGURE 6b represents the process output waveform,

FIGURE 6c represents the model output waveform,

FIGURE 6d represents the waveform on the output of the summer or the error signal,

FIGURE 6e represents the waveform of the integral of the error squared with respect to time.

GENERAL DESCRIPTION The present invention relates to the use of non-interacting elements as a rapid method for determining process dynamics of a system. The rapid process simulator and the method of employment thereof is considered to be particularly adaptable for use with linear stable processes whose dynamic characteristics are unknown. The unknown p1 ocess is generally compared with an orthogonal model. The model is formulated with the idea of choosing a pulse input in such a way to facilitate the construction of the system. The frequency analogs of the well known Laguerre polynomials are particularly suitable as a choice for the simulator.

A five term orthogonal set has been found to be sufficiently adequate as a model for the simulator. A disturbing pulse is injected into an open loop system of the process and into the developed model of the orthogonal functions. The responses produced by the open loop system of the process and the orthogonal model is then compared by subtracting the response of the orthogonal model from the response of the unknown process which produces an error signal. The error signal is then squared in a conventional squarer to produce the square of the signal and then integrated to obtain the integral of the error signal. The process can be repeated with new values of the coeflicient until minimization of the integral error squared is obtained. This integral error squared can be conveniently depicted on a digital voltmeter. Moreover, the model and the integrator can be provided with reset pulses from the triangular and pulse wave generators which are used to provide the disturbing pulses. When the best fit is obtained by observing the time histories of both the unknown system and the model to the pulse input along with the value of the integral, the coeicients are read out and a simple expression is obtained for the input-output pair of interest.

.In the past, sinusoidal waves have been used as a .means of providing disturbing pulses. The sinusoidal wave as a means of providing a disturbing pulse is no longer employed, inasmuch as a triangular wave generator providing a signal to a square wave sampler and a ramp wave sampler will provide all of the harmonics necessary for the simulator. Accordingly, the rapid process simulator uses a triangular wave generator for developing pulses which are, in turn, transmitted to a pulse generator. The pulse generator employs a pair of off-on switching circuits, the rst of which functionally serves as a square wave generator or so-called sampler or shaper and a ramp wave generator or so-called sampler or shaperf The second off-on circuit functionally serves as a delay square wave sampler and delay ramp wave sampler for handling transport delay times, that is where the input; pulse to the model is delayed so that the output of the unknown system and the model will begin at coincident times. While the pulse generator actually includes off-on switching circuits, these switching circuits can be functionally realized in the manner as described, and more-y over each of the switching circuits is provided with pulse selectors for selecting a ramp wave or square wave as desired. Furthermore, each of the sets of square wave and ramp wave samplers is designed to provide signals to an electrical-pneumatic converter and range selector or pneumatic range selector. For example an electricalto-pneumatic transducer can be employed for providing a pneumatic signal in the process or an electrical signal can be injected directly into the process and into the orthogonal model. Similarly, the output of the process can again be converted to an electrical signal for comparison with a model readout.

Once it has been established that the simple linear model is sufficiently accurate to describe the process, it is routine to determine the correct values of integral action, proportional action derivative action on a stand-- ard process controller. Such methods as the root locus method and methods of Bode and Black, and Nyquist, etc. directly apply. Furthermore, the open loop adaptive control function can be determined by establishing a simple linear model for different levels of operation. Thus, the necessary controller characteristics for the entire set of model functions can be found as a function of these levels and with the application of these characteristics the process will always be operating at an optimum.

The chemical systems are almost always non-oscillatory, that is, the transfer function describing the dynamics are a series of time constants in the denominator with real roots. After a mathematical expression for the unknown process has been obtained through acquiring the coecient of the parameter of the model, it is possible to formulate a procedure to obtain a slightly more damped closed loop response than the one cycle, quarter amplitude ratio or minimum area squared criteria. iStability apart, this is done by setting the transfer function of the closed loop system with unknown controller constants equal to unity and rewriting the expression in descending powers in the denominator and numerator. One then equates the coefcients of like powers and solves for the controller characteristics.

As used. herein, the term orthogonal as applied to two unweighted transfer functions f1(x) and f2(x) generally in La Place form, between the limits of --oo and. -i-co is dened by a mathematical expression In addition if f1(x) and f2(x) are orthonormal, the following relationship is true In these expressions j`1(x) and f2(x) are the con-I jugates of the real functions f1(x) and f2(x) respectively, and include real and imaginary components as JJRxjIx) and j2(Rx]Ix). When an orthogonal set of functions is normalized, by senting it will satisfy the second equation Where the integral of the functions of x is equal to 1.

DETAILED 'DESCRIPTION Referring now in more detail and by reference characters to the drawings which illustrate a preferred embodiments of the present invention, A designates a rapid process simulator substantially as illustrated in its compact portable form in the front plan View of -FIGURE 1.

The rapid process simulator A can be designed as a rather small compact unit which is portable and easily transportable to various locations. Moreover, it can be designed so that it is capable of being fitted into any of the standard electrical component racks. As illustrated in FIGURE 1, the rapid process simulator A is enclosed within a metallic cabinet 1 which is snugly iitted within a portable housing 2 having a handle-forming strap 3 on the upper end thereof. The housing 2 is centrally provided with a large rectangular aperture 4 on the front face for' slidably accommodating the cabinet 1 of the rapid process simulator A. The outer housing 2 may -be conventionally provided with tracks and rollers, as desired, for providing easy shifting movement of the cabinet 1 into and out of the portable housing 2. This construction is conventional and is, therefore, not described in detail herein.

The cabinet 1 of the rapid process simulator A forms a control panel 5 upon which are mounted a series of dials, switches and recorders, to be hereinafter described in more detail. The control panel 5 is slightly recessed and extending around the periphery thereof on the cabinet 4 is a'peripheral rim 6. A series of spaced conventional lock mechanisms (not shown) may be mounted on the front face of the housing and which engage the rim 6 on the cabinet l. These conventional lock mechanisms may be swingable from the locked position so that the cabinet 1 may be removed from the housing 2. Mount. ed on a side panel of the housing 2 is a pair of multi-station terminal connectors -8 and a pair of pneumatic fittings 9. Similarly extending from the rear wall of the housing 2 is a cord set 10 for connection to a suitable source of electrical current (not shown).

SCHEMATIC BLOCK DIAGRAM FIGURE 2 provides a schematic illustration in block diagram of the operative connection between the various component systems forming part of the rapid process simulator and its operative connection to the process with unknown conditions. The rapid process simulator A includes a regulated power supply S which supplies power for all circuits in all blocks of the instrument. A main olfon power switch s as illustrated in FIGURE 1, is internally wired in this unit and mounted on the contorl panel 5. The simulator A also includes a triangular wave generator 11 for producing pulses to be injected into an unknown process P having unknown parameters and into a model of orthogonal functions M. The triangular wave generator 11 also includes a compute time mechanism 12 lfor adjusting the time period of the simulation. The triangular wave generator 11 provides the time lcontrolling signal which is transmitted to a pulse generator 13, as illustrated in FIGURES 2 and 3a. By reference to FIG- URE 3b, it can be seen that the pulse generator 13 includes a pair of olf-on bistable switching circuits 14, 15

which are more fully described in detail hereinafter. However, in the block diagram of FIGURE 12, the pulse generator 13 is illustrated as including a square wave generator or so-called sampler I6 and a ramp wave generator or sacalled sampler 17. The pulse generator 13 is also illustrated as including a delay square wave generator or sampler 18 and a delay ramp wave generator or sampler 19. In terms of circuitry involved, the samplers 16 and 17 are included in the switching circuit 15. The triangular wave generator 11 is illustrated as including four samplers for ease of explanation of the invention since in functional form the generator 11 operates as though it included four samplers or wave generators. The triangular wave generator 11 produces a triangular wave which is fed to the samplers 16, 17, 18 and 19, all in the manner as schematically illustrated in FIGURE 2. The output of the triangular Wave is always positive except for a short period when it is neagtive at the end of the compute cycle for resetting.

The square wave sampler 16 and the ramp wave sampler 17 are provided with electrical output lines 20, 21 respectively Iwhich can be connected to an electrical range selector 22 for converting the signal into a desired electrical input range. The output lines 20, 21 may also be connected to an electrical-to-process converter 23 which is capable of changing the electrical output into a desired process input. The process input, of course, may be a pneumatic input or electromechanical input and the converter 23 is designed to convert the electrical input thereof to the desired process input. As illustrated in FIGURE 2, the electrical-to-process converter 23` or so-called E-P converter, is a convnetional electropneumatic transducer capable of converting electrical signals into proportional pneumatic signals. Furthermore by reference to FIGURE 3 f, it can be seen that the electrical-to-process converter 23 and the electrical range selector 22 are constructed with common circuitry and form a unitary electrical and pneumatic range selector. However, the electrical and pneumatic range selector is illustrated with the range selector 22 and converter 23 in block form in FIGURE 2 since the selector serves both functions. This input signal which may be either in pneumatic or electrical form is thereupon inserted into the process P in order to disturb the condition of the process. The signal is also inserted into the model M of orthogonal functions. However, .it may be ldesirable to provide a delayed model signal in certain cases. Accordingly, the delay square wave sampler 18 and the delay ramp Wave sampler 19 are provided with outputs 24, 25 which are, in turn, optionally connected to the input of the model M for providing a signal to the model M of orthogonal functions.

A two-way sampler switch 26 is connected across the output lines 20, 21 for selection of either a square wave signal or a ramp wave signal. The switch 26 is mounted on the control panel 5 in the manner as illustrated in FIGURE l. The switch 26 is, in turn, electrically connected to a switch 27 which serves as an electricalpneumatic selection switch, the latter also being mounted on the control panel 5. By reference to FIGURE 2, it can -be seen that the switch 26 functionally provides selection between the square wave sampler 16 and the ramp wave sampler 17. The selector switch 27 provides selection between the electrical range selector 22 and the processrange converter 23 for providing a desired pulse. The output lines 24, 25 are also provided with a sampler selection switch 28 similar to the previously described switch 26 for selecting either a delay square wave or a delay ramp wave from the samplers 18, 19 respectively. The switch 28 is mechanically connected to and operable with the switch 26 and is, therefore, not mounted on the control panel. In other words, when the square wave sampler 16 is functionally employed, the delay square wave sampler 18 may be functionally employed Similarly, when the ramp wave sampler 17 is functionally employed,

the delay ramp wave sampler 19 may be employed. A two-way switch 29 is mounted on the control panel 5 and is designed to functionally interpose the delay samplers 18, 19 in the circuit by providing a delayed pulse to the model M as illustrated in FIGURE 2. It may be desirable to provide an oscillatory transient on the signal in the model function M if the process P contained such transients and therefore, an oscillatory transients generator T is provided. The oscillatory transients generator T is connected to the model of orthogonal functions M and into the input line to the model M. A switch 30, which is mounted on the control panel S provides optional interposition of the oscillatory transients generator T in the system in the manner as schematically illustrated in FIG URE 2.

The input signals are designed to upset the process and, thereby, produce a process output signal which is, in turn, transmitted to a process to electrical signal converter 31 or so-called P-E converter. This converter is similar to the converter 23 and may be a conventional pressure transducer. If the process P is electrical in nature and the output thereof is electrical, the output signal is transmitted directly to an electrical range selector converter 32 substantially similar to the previously described selector 22. The electrical range converter 32 and the process to electrical signal converter 31 are functionally illustrated in the block diagram of FIGURE 2 as separate components for purposes of more fully describing the present invention. However, it can be seen that these two components are partially combined to form an electrical and pneumatic range selector as illustrated in FIG- URE 3e. lt should also be noted that a selector switch is not employed for the output signals from the process since only an electrical or a pneumatic signal may be transmitted therefrom.

The combined pneumatic and electric signal converter 31 transmits the output signal to one terminal of an adder or summer or so-called totalizer 33 and the output signal of the model M is transmitted to the other terminal of the totalizer 33. An output tap 34 from the process to electrical converter 31 and an output tap 34 ffrom the range selector converter 32 are connected to opposite terminals of an electrical-pneumatic selector switch 27 Accordingly, it is possible to select the proper signal from the process P for transmission to the adder 33. It should be recognized that the switches 27, 27 are not connected in common since it is possible to introduce an input signal which differs in kind from the output signal of the process. An output tap 35 on the output side of the model M will provide the output signal of the model M. The adder 33 is designed to combine the output signal of the model M of the orthogonal functions with the process signal and, thereby provide an error signal which can be tapped at 36 for optical illustration thereof. The error signal from the adder 33 is transmitted to a conventional squarer 37 in order to obtain the square of the error signal with respect to time. The signal from the squarer 37 is then transmitted to a conventional integrator 38 often referred to as an evaluation means where the square of the error signal is integrated with respect to time and, in turn, is transmitted to a four place digital voltmeter 39. The voltmeter 39 is provided with a four digit readout panel 39 mounted on the control panel 5, for direct reading output. The signal from the process P at the taps 34, 34', the output signal from the model M at the tap 35 and the error signal at the tap 36 can be graphically illustrated on a three channel oscillographic recorder 40 or so-called recording oscillograph as illustrated in FIGURE 1. This recorder is conventional in its construction and is, therefore, not described in further ldetail herein. The integrator 38 which is conventional in its construction is also electrically connected to the triangular wave generator 13 for receiving reset pulses. The digital voltmeter 39, which is also conventional, in its construction is normally operating at its own repetition rate and, therefore, a number of readings are monitored during one compute cycle. After the output of the error signal, which has been integrated, is depicted on the digital voltmeter 39, the triangular wave generator 11 is designed to provide reset pulses to the integrator 38, the model M and the oscil latory transients generator T for resetting each of these components to a zero position.

Thus, in the operation of the system, the unknown process which is to be analyzed is selected. This process may be pneumatic, electrical, mechanical, biological, etc.; the only criterion being that the process must be capable of providing an electrical or pneumatic output signal and accepting an electrical or pneumatic input signal. The compute time mechanism 12 is set to a desired time period before pulses are injected into the process and into the model of orthogonal functions. This time compute mechanism 12 controls the frequency of the triangular wave generator 11 which in turn provides a triangular Wave signal to each of the square wave samplers 16, 18 and to each of the ramp wave samplers 17, 19. If for the type of process being simulated, it is desirable to employ a square wave, the switch 26 is shifted to the position where it communicates with the square wave sampler outlet line 20. If it is desired to employ a delayed ramp or square wave for the model M, the switch 29 may be shifted to the position where the transport delay samplers 18, 19 are interposed in the circuit. On the other hand, if the system is such that a delayed wave to the model is not necessary, the switch 29 is switched to the od position so that the transport delay samplers 18, 19 are inoperable, that is the off-on switching circuit 15 is rendered ineffective through the switch 29. After the selection between the square wave and ramp wave sam plers, the switch 27 is shifted to the converter 23 or the range selector 22. The converter 23 is employed if the signal is one other than an electrical signal. However, if the input signal is an electrical signal, the range selector 22 would be employed. If an input signal is transmitted to the process and by inspection of the recorder, the process output is found to contain oscillatory transients the oscillatory transients generator T may be interposed in the system by closing the switch 30, that is shifting the switch 30 to either plus or minus position.

The responses produced by the open loop system of' this process P and the orthogonal model M is compared by subtracting the response of the orthogonal model. M from the response of the process P at the summer 33, which in turn produces an error signal at 36. The signal from the process can be tapped at 34, 34' and the signal from the model can be tapped at 35. If the signal from the process P is other than an electrical signal, it is con-y verted to an electrical signal in the P-E converter 31. The error signal on the output of the adder 33 is then transmitted to the squarer 37 where it is squared. The integral of the error squared is then obtained. in the integrater 38 and this error squared signal is transferred to the digital voltmeter 39 where an output reading is obtained. By observing the time histories of both the unknown process P and the model M, the coefficients of the parameters of the model with respect to time are obtained and at the smallest error signal, a simple expression is obtained for the input-output pair of interest.

Having described the overall operation of the various component systems, it is possible to describe each of the component systems in detail.

TRIANGULAR WAVE GENERATOR The rst component system is the triangular wave generator which is schematically illustrated in FIGURE 3a. The triangular wave generator 11 is connected to the power supply S and receives therefrom a plus reference signal and a minus reference signal by means of refer ence signal conductors 41, 42 respectively. The conduc-J tors 41, 42 are connected across contracts 43, 43 of a relay 44. Movable between the contacts 43, 43 is a contace` arm 45 which is connected directly to the compute time control mechanism 12. A standard potentiometer 46 forms part of the compute time control mechanism 12 and a control dial 46 is mechanically connected thereto and mounted on the control panel for operation of the same. The movable arm of the potentiometer 46 which forms part of the compute time control mechanism 12 is connected through an integrator input resistor 47 to a reset-operate switch or so-called mode control switch 48 forming part of a Miller Integrator 49. The Miller Integrator 49 includes an operational amplifier 50` and connected in parallel therewith is a series of integrating capacitors 51. A series of time scale switches 52 are also connected in parallel therewith and are designed to control the integration rate of the integrator 49. A reset resistor 53.1's also connected in parallel to the amplifier 50 and is connected to one terminal of the reset-operate switch 48 for the purpose of resetting the integrator 49 to zero. The reset-operate switch 48 is actually a mode control and is mounted on the control panel 5 in the manner as shown in FIGURE l. In order to make time scale changes and get proper input and output characteristics, the reset-'operate switch 48 is set to the reset position, that is the lower position, reference being made to FIG- URE 3a.. When shifted to the operate position, that is the upperposition, reference being made to FIGURE 3a, the integrator and associated circuitry hereinafter described will continually provide triangular wave signals.

Also connected across the plus and minus reference conductors 41, 42 are a pair of voltage dividing variable resistors 54, 55, the movable arms of which are connected to contacts 56, 56', respectively. A contact arm 57 movable between the contacts 56, 56 is connected through an input ,resistor 58 to a summing junction 59 of an operational amplifier 60. An input resistor 61 is located on the opposite side of the summing junction 59 with respect to the amplifier 60. In effect, a comparison 0f voltage across the input resistors 58, 61 is made with the summing junction 59. The voltage sum is amplified by the amplifier 60 and if the sign is correct, the signal is passed through a diode 62 to a relay coil 63 forming part of the relay 44. If the sign is not correct, the Voltage will not pass through the diode 62 but is shunted to the summing junction 59 through a diode 64 connected in parallel with the amplifier 60;

A three position pulse direction switch 65 having a plus position, a minus position and an off position @TV-is connected across the reference conductors 41, 42. The switch 65 is mounted on the control panel 5 and the movable element thereof is connected to a contact 66 which is cooperative with a movable contact arm 67, the latter being connected to a height/ rate potentiometer 68. A height/ rate control dial 69 is mechanically connected to the potentiometer 68 for operating the same and is mounted on the control panel 5.

When the main power switch s is closed, the reference conductors 41, 42 will become energized. The contacts 43, 43 and 56, 56 will also become energized. If the pulse direction switch 65 is moved to the positive position, the contact 66 is energized. The de-energized position of the relay 44 is illustrated in FIGURE 3a. If the reset-operate switch 48 is in the operate position, the integrator 49 will produce a positively increasing output signal. This voltage is compared by the input resistors 58, 61 to the voltage on the variable resistor 54. When the output voltage on the integrator 49 reaches a value slightly more positive than the negative value on the variable resistor 54, then the sign of the amplifier l60 is negative allowing current to pass through the diode 62 and thus energizing the coil 63 of the relay 44. Energization of the coil 63 will cause the contact arms 45, 57 to shift t0 the contacts 43', 56 respectively. This changes the value of the input to the integrator 49 changing the sense thereof so that it becomes increasingly negative. The output voltage of the integrator 49 becomes increasingly negative until the voltge compared at the summing junction 59 is slightly negative causing the output of the amplifier to be positive. Since the diode 62 will not accept positive voltages, this causes the coil 63 to become de-energized. As a result thereof, the contact arms 45, A57 and 67 will shift to their upper position, reference being made to FIGURE 3a. The diode 64 is connected so that the amplifier 60 receives negative feedback when the output thereof attempts to become positive. The presence of the contacts 66 insures that a pulse will only be generated when the output of the integrator 49 is increasing positively. By reference to FIGURE 3a, it can be seen that the relay coil 63, the diodes 62, 64, the amplifier 60 and the input resistors 58, 61 form a relay comparator circuit which is present in many other component systems of the present invention. This relay comparator circuit is similar to the relay comparator circuit used in the other systems and is, therefore, not described in detail hereinafter. However, it should be recognized that more input resistors can be employed for comparing more than two circuits.

MODE CONTROL CIRCUIT Many reset relay circuits are present in the component systems forming part of the rapid process simulator such as the model M, the oscillatory transients generator T and the integrator 38. A mode control circuit, substantially as illustrated in FIGURE 3a, is provided for rcsetting each of these component systems to initial conditions after each compute cycle. The mode control circuit includes a pair of low voltage relay power conductors 69, 70. This relay power is supplied to the various relay coils by means `of closing the manual reset operate switch 48 or automatically at the end of the compute cycle by means of contacts 71, 71' forming part of a relay 72. The relay 72 is energized by a relay comparator circuit 73 similar to the relay comparator circuit in the triangular wave generator 11. When the triangular wave becomes slightly negative, the relay 72 will become energized causing the contacts 71 to close and this, in turn, will energize all other reset relay coils in all component systems, thereby resetting theassociated component systems. The operative connection to the other component systems of the mode control circuit will be more fully hereinafter described in detail.

A typical relay comparator circuit as employed in the present invention is illustrated in FIGURE 3a and includes a relay coil such as the coil 72 which operates a set of contacts similar to the contacts 71, 71. The typical relay comparator circuit, therefore, includes the relay coil 72, an operational amplifier 74, a pair of diodes 75, 76, and at least two input resistors 77, 77'. The diode 75 is connected in parallel with the operational amplifier 74 and the diode 76 is connected in series with the amplifier 74 and the relay coil 72. In its operation, the amplifier 7-4 will amplify a difference signal measured by the input resistors 77, 77. If the difference signal is of the proper polarity, the diode 76 will conduct, thereby energizing the coil 72. If the difference signal is of an undesired polarity, the diode 76 will not conduct and the diode 75 will conduct thereby maintaining a low output from the amplifier 74 preventing energization of the relay 72. Connected to the resistor 77 is an internally disposed reference potentiometer 77" for providing a slightly positive voltage so that the relay 72 will be energized when the triangular wave is slightly negative. By means of this circuit, it is possible to compare a selected fixed or variable voltage to a reference voltage and performing either of two functions depending -upon the difference in the magnitude of these two voltages.

PULSE GENERATOR The functional operation of the pulse generator 13 is more fully illustrated in FIGURE 2 and the operation thereof in terms of function is described hereinabove. The

1 l components forming part of the pulse generator are more fully illustrated in FIGURE 3b and include four relay comparator circuits 78, 79, 80 and 81. Each of these relay comparator circuits 78, 79, 80 and 81 is substantially similar to the relay comparator circuit 73. These relay comparator circuits are also substantially similar to the comparator circuit in the triangular wave generator 11 except that the relays are energized on a positive signal whereas the relay in the comparator circuit of the triangular wave generator was energized on a negative signal.

The input of each of the relay comparator circuits 78, 79, 80 and 81 is connected in common to the output of the integrator 49. Moreover, another input of each of the relay comparator circuits 78, 79, 80 and 81 is connected to the movable element of a delay control potentiometer 82. One terminal of the delay control potentiometer 82 is connected to a `minus reference conductor 83 which in turn receives power from the power supply S. The opposite terminal of the potentiometer 82 is grounded. The delay control potentiometer 82 is operable by a delay control dial 84 mounted on the control panel 5 and is designed to provide a delay in the time that the first disturbing pulse commences after the operate switch is shifted to the operate position.

The relay comparator circuits 79, 81 have additional input resistors `87, 88 which are connected in common and to the movable arm 85 of a duration control potentiometer 86. One terminal of the duration control potentiometer 86 is connected to the negative reference conductor 83 and the opposite terminal thereof is grounded. The movable arm 85 of the duration control potentiometer 86 is mechanically connected to and operably by a duration control dial 86', the latter being mounted on the control panel 5. The duration control potentiometer 86 is designed to provide any desired pulse widths for both square and ramp wave pulses and associated delayed square and ramp wave pulses. The relay comparator circuits 80, 81 and additional input resistors 89, 90 respectively, are connected in common to the movable arm 91 of a transport delay control potentiometer 92. The movable arm 91 of the potentiometer 92 is mechanically connected to and operable by a transport delay control dial 93, which is mounted on the control panel 5. The transport delay control potentiometer 92 is designed to control the time delay between the initiation of a disturbing pulse to the model M after the injection of a disturbing pulse into the process P. The relationship between the disturbing pulse transmitted to the process P and the pulse transmitted to the model M for comparison is more fully illustrated in FIGURE 2.

The relay comparator 78 includes a set of normally open contacts 94, 94 and the relay comparator 79 includes a pair of normally closed contacts 95 and a normally open contact 95. Similarly, the relay comparator circuit 80 includes a pair of normally closed contacts 96 and a normally open contact 96 and the relay comparator circuit 91 includes a pair of normally closed contacts 97 and a normally open contact 97. The normally open contact 94 is connected through an input resistor 98, through the normally closed contact 95, and to the input of a medium gain operational amplifier 99. The movable arm of the selector switch 26 is connected to the output side of the amplifier 99 and to the normally open contact 95'. Connected to the input side of the amplifier 99 is a feedback resistor 100 and also connected in parallel with the amplifier 99 is a feedback capacitor 101. Thus, when the sampler switch 26 is shifted to the upper position, the feedback resistor 100 is inserted in the circuit and the amplifier 99 operates as an inverter. When the switch 26 is shifted to the lower position, the capacitor 101 is inserted in the circuit and the amplifier 99 operates as an integrator. The operational amplifier 99, the feedback resistor 100 and the capacitor 101, in combination with the selector switch 26 constitutes a pulse selector.

A similar pulse selector is connected to the relay corn-y parator circuits 80, 81 The contact 96 is connected through an input resistor 102, through the normally closed contact 97 to the input of a medium gain operational amplifier 103. The selector switch 28 is connected to the output of the amplifier 103 and to the normally open contact 97. Connected to the input of the amplifier 103 is a feedback resistor 104 and a feedback capacitor 105. As previously indicated, the switches 26, 28 are tganged or connected in common, so that they operate in unison. Thus when the switch 26 is shifted to the upper position, the switch 28 will be shifted to the upper position and the amplifiers 99, 103 will both function as inverters. Similarly, when the switch 26 is shifted to the lower position, the switch 28 will be shifted to the lower position, reference being `made to FIGURE 3b and the amplifiers 99, 103 will serve as integrators. By further reference to FIGURE 3b, it can be seen that the output of the operational amplifiers 99, 103 is connected to the transport delay switch 29.

It can be seen that the relay comparator circuits 78, 79 combined with the associated pulse selector circuit forms the square wave and ramp wave selectors 16, 17. Similarly, the relay comparator circuits 80, 81 and the associated pulse selector circuit form the delay square wave and delay ramp wave selectors. ln its operation, the triangular wave will increase positively in slope to a point. where it equals the value set on the delay control potentiometer 82 at which time the contact 94" closes, thereby feeding a voltage from the height/ rate potentiometer 68 to the input resistor 98. Since the contacts 95 are closed at this time, this signal will be transmitted to the amplifier 99. In similar manner, when the positively increasing triangular wave voltage equals the combined voltages maintained on the delay control potentiometer and the duration potentiometer the contact 95 will close. This will remove the input to the amplifier 99 and resets the amplifier 99 to a zero position. During the time that the triangular wave is increasing positively, a constant amplitude signal is transmitted to the relay comparator circuits 78, 80 from the height/rate control potentiometer 68. Thus, by the continued switching of the on-ofi switching circuit 14, the adjusted constant amplitude signal to the relay comparator circuit 78 will produce a square lwave when the selector switch 26 is shifted to the square wave position, that is the upper position. l'n this manner, the amplifier 99 serves as a coupler. When the switch 26 is shifted to the lower position, lthat is the GLramp wave position, the amplifier 99 will serve as an integratorcoupler and the constant amplitude Signal supplied to the relay comparator circuit 78 will form a ramp wave when integrated.

The off-on switching circuit 15 operates in similar manner to the off-on switching circuit 14. More specifically, the relay comparator circuits 80, 81 operate in a manner similar to the operation of the relay circuits 78, 79. When the voltage at the contact 96 is equal to the combined voltage at the delay control potentiometer 82 and the transport delay control potentiometer 92. the Contact 96 will close. The same signal fed to the contact 94P is fed to the contact 96 and the input resistorl 102. This signal is transmitted to the amplifier 103. Therefore when the selector switch 28 is shifted to the upper position, the amplifier 103 serves as an inverter and a square lwave signal is produced. When the selector switch 28 is shifted to the lower position, the amplifier 103 serves as integrator and a ramp wave signal is produced. However, the signal output of the amplifier 103 is delayed more than with respect to the amplifier 99. This occurs as a result of the interposition of the resistors 89, in the circuit, 'thereby causing the relay comparator circuits 80, 81 to operate on a higher voltage of the triangular wave signal.

From the above analysis, it can "be seen that by increasing the voltage on the delay control potentiometer 82, a higher voltage is required at the other input of the comparator circuit 78 to cause the contact 94' to close. This will create a -greater delay in the time that the square Wave commences. In similar manner, an increase of voltage in the duration control potentiometer y86 will require a greater voltage on the triangular wave input to the relay comparator circuit 79 before the same will switch. Also, an. increase in voltage on the transport delay potentiometer 92 will necessitate a larger Voltage on the triangular wave input to the relay comparator circuits 80, 81 before the same will switch. In this manner, it is possible to control the delay and duration of the initial square wave or ramp wave signal and to control the delay, duration and transport time of the second square or ramp Wave signal. By shifting the switch 29 to the lower position,

that is the son position, the transport delay square andl ramp wave selectors 18, 19 are inserted in the circuit. By shifting the switch 29 to the upper position, that is the off position, no transport delay is created and square or ramp wave signals will be fed simultaneously to the model M, the oscillatory transients -generator T and the process P.

MODEL The model is designed to match an unknown process in order to determine the parameters of the dynamic characteristics of the process. In the rapid process simulator A, the following mathematical representation of the model has been found to be adequate for the vast number of mechanical, electrical, and electromechanical processes encountered.,

It can be seen that the mathematical expression of theV model includes parameters in a fifth order system of which five are amplitude coefficients and live are time constants. The mathematical theory for the derivation of the circuit requirements to be the analogue of this expression isset forth hereinafter-However, it should be recognized that a higher order system could be employed in some cases where it is necessary to obtain a more accurate simulation of the system. It should also be recognized that the model herein described is orthogonal to a unit input function. For any other practical input pulses, the degree of orthogonality is reduced slightly. This reduction in orthogonality by employment of other than unit input pulses has produced no problem and the model set forth above has been found to be adequate. If it is desired to use -a greater degree of mathematical rigor, it is possible to adjust the model within the scope of this invention by altering the present m-odel and testing the alteration thereof mathematically for orthogonality. The method of altering the model will be more fully `understood by reference to the mahemaical theory of operation of the rapid process simulator hereinafter set forth.

The present model includes five amplitude constants a. ag, a4, af., and tive time constants T1, T2, T3, T4, T5. The circuitry in FIGURES 3c and 3d, which is a representation of this mathematical model, is designed to vprovide direct readouts for each of the ten parameters.

The circuit of the model, therefore, includes ve modules 106, 107, 108, 109, 110, each of which produces a readout of one amplitude coeicient and one time constant for each order. Each of the modules G-110 is substantially similar in construction and operation and, therefore, only the module 106 will be described in detail. The module 106 includes a summer 111 formed by an operational amplifier 112, an input resistor 113 and a feedback resistor 114. The amplifier 112 also includes an input resistor 115. It can be seen that the input resistor 113 is connected directly to the output from the pulse generator 13. The output of the operational amplier 112 is connected to one terminal of a time constant potentiometer 116, the other terminal of the potentiometer 116 being grounded. The potentiometer 116 is provided with a control dial 116' mounted on the control panel5. The movable element of the potentiometer 116 is connected to the input resistance 117 of an integrator 118. The integrator 118 includes an operational amplifier 119 and a feedback capacitor 120. Interposed between the movable element of the potentiometer 116 and the input of the operational amplifier 119 are a pair of reset contacts 121, which are operable by a relay reset coil 122. The reset relay coil 122 is operatively connected to and operable by the mode control circuit described hereinabove, Also connected in feedback relationship with the contact 121 is a feedback resistor 123, which is designed to reset the integrator to a zero position after each compute cycle. The module 106 also includes an inverter y124, which is connected to the output side of the operational amplifier 119. The inverter 124 includes an operational amplifier 125 having an input resistor 126 and a feedback resistor 127. The output of the inverter 124 is connected through the resistor 115 to the input of the summer 111.

The input from the pulse generator 13 feeding the summer 111 through the input resistor 113, in conjunction with the integrator 118 and the inverter 124, will simulate the transfer function of a system described by a tirst order dilferential equation. Connected in parallel with the inverter is a direction switch 128 having a plus position, a minus and an olf position. The direction switch 128 is designed to provide proper sense of the module simulation with regard to the unknown process.

The direction switch 128 is mounted on the control panel 5 for operation thereof. At the output of the switch 128, the circuit thus far described will have transfer characteristics of a irst order system with an amplitude coeicient of plus or minus one. In order to provide numbers other than one as an amplitude coetiicient, the movable element of the switch 128 is connected to an amplitude potentiometer 129 having a control dial 129 mount'd on the control panel 5. The movable element of the potentiometer 129 is connected through anfinput resistor 130 to a summer or totalizer 131. The totalizer 131 may have a gain greater than one and of any desired value on the various inputs as constructed. The potentiometer 129 is connected so that it can select any portion of the gain of the totalizer 131. The gain bet-Ween the input of the module 106 and the output of the switch 128 is one. Thepotentiometer 129 provides a selection of any number less than one to be multiplied by the xed gain in the associated input of the totalizer 131. The value of a is, therefore, equivalent to the position of the potentiometer 129 multiplied by the xed gain of the totalizer 131 By reference to FIGURES 3c and 3d, it can be seen that each of the modules 106-110 is substantially similar in construction. The method of calculating the amplitude coefficient in each module 107-110 is substantially similar to the method employed in determining the amplitude coeicient a1 in the module 106. Thus, the module 107 is provided with a direction switch 132 having an off position, a plus position and a minus position. The direction switch 132 is designed to provide the proper sense of the amplitude coefficient a2 in the module 107 with regard to the unknown process. Each of the modules 108, 109, is also provided with direction switches 133, 134 and 13S respectively. Each of the direction switches 133, 134 and 135 is designed to provide the proper senses of the amplitude coefficients a3, a4, a5 in each of the modules 108, 109, 110 with regard to the unknown process. Moreover, by reference to FIGURE 1, it can be seen that each of the direction switches 132-135 is mounted on the control panel 5. The movable elements of each of the direction switches 132, 133, 134 and 135 are connected to amplitude potentiometers 136, 137, 138 and 139 respectively, having control dials and all of which are mounted on the control panel 5. Each of the potentiometers 136-139 is similar to the potentiometer 129 and are connected through input resistors 140, 141, 142 and 143 respectively to the totalizer 131.

The totalizer 131 comprises a medium gain operational amplifier 144 and a feedback resistor 145 connected in parallel therewith. The totalizer 131 also includes the five input resistors 130, 140, 141, 142 and 143. The values of the various input resistors 130 and 140-143 are sized to give a proper gain constant with respect to the feedback resistor 145 so that the various ranges of the amplitude coefiicients r11-a5 can be assigned to the respective potentiometers 129 and 136-139. It can thus be seen that the values of each of a2, a3, a4, a is equivalent to the position of the respective potentiometers 136, 137, 138 and 139 multiplied by the fixed gain of the totalizer 131.

As indicated above, each of the modules 106-110 includes a summer, an integrator and an inverter. The summer of the module 107 includes an amplifier 146 having an input resistor 147 which is connected to the output of the integrator 118 in the module 106. The amplifier 146 is also provided with an input resistor 148 which is connected to the output of the summer 111 in the module 106. In similar manner, the module 108 is provided with an amplifier 149, which is connected through input resistors 150, 151 to the outputs of the integrator and summer respectively of the module 107. The summer of the module 109 is provided with an operational amplifier 152, which is connected through input resistors 153, 154 to the outputs of the integrator and summer respectively of the module 108, Finally, the summer of the module 110 is provided with an amplifier 155, which is connected through input resistors 156, 157 to the outputs of the integrator and summer, respectively, of the module 109. Each of the modules 106-110 would provide the same form of input over output characteristic if the connecting input resistors 148, 151, 154 and 157 were removed. The transfer function of thee integrator is l/s. From a study of the feedback relations in each of the -modules 106-110, it can be seen that the resistor 148 supplies the term [-Tzs] and the resistor 147 provides the term '1. TlS-il when combined with the associated summer in the model equation. In similar manner, the resistor 151 provides the term [-Tzs] and the resistor 150 provides the term T28-il when combined with the associated summer; the resistor 154 supplies the term [-T3s], the resistor 153 supplies the term when combined with the associated summer; the resistor 157 supplies the term [-T4s] and the resistor 156 supplies the term T4Sil when combined with the associated summer, in the model equation. The module 110 supplies the value It can be seen that by going through each module the output of said module is equivalent to the input of the module multiplied by the characteristic function of said module. Thus, the output of the fifth module 110 is the 16 product of all modules 106-110 characteristic function times the input signal.

By further analysis of the circuit in FIGURES 3c and 3d, it can be seen that the output of the first module 106 produces the normalized first term in the orthogonal set, namely TDS-i* 1 the output of the module 107 produces the normalized second term in the orthogonal set, namely (l-Tis) '(T1s+1)(T2s+l) the output of the module 108 produces the normalized third term in the orthogonal set, namely (T1S+1)(T2S+1)(T3S+l) the output of the fourth module 109 produces the norn malized fourth term in the orthogonal set, namely and the output of the fifth module 110 produces the normalized fifth term in the orthogonal set, namely The terms in this orthogonal set are orthonormal because each amplitude coefficient a is one in the above case. In other words when all modules are connected together in the manner as shown in FIGURES 3c and 3d with the exclusion of the amplitude potentiometer, an orthonormal set is produced. When the totalizer 131 is included and the a functions are not equal to one, an orthogonal set is produced.

The summer ampliers 146, 149, 152 and 155 in each of the modules 107, 108, 109, 110 has outputs connected directly to time constant -potentiometers 158, 159, 160, 161 respectively. The opposite terminals of each of these potentiometers 158-161 are grounded. Furthermore, the movable arms of each of the potentiometers 158-161 are connected to reset contacts 162, 163, 164 and 165. The time constant potentiometers 158, 159, and 161 as well as the time constant potentiometer 116 are mounted on the control panel 5 in the manner as illustrated in FIGURE 1.

lIn order to understand the operation of each of the modules 106-110 in determining the time constant T, it is necessary to consider each of these modules separated at the connecting resistors such as the input resistors 147, 148. Thus, the module 106 would be considered without the resistors 147, 148 and the module 107 would be considered as including the input resistors 147', 148 and ex'I cluding the input resistors 150, 151. Each of the modules 106-110 when considered in the autonomous state Operates in like manner and, therefore, the operation of one module is described in detail herein.

Considering the module 106, the module includes the summer 111, the time constant potentiometer 116, the integrator 118 and the inverter 124. In order to understand the theory of the production of the time constant, it is necessary to briey set forth the mathematical theory of each module. The summer 111 takes each of two input signals, combines the signals, inverts the combined signal and presents the results on its output. The potentiometer 116 receives the output signal from the summer 111 and produces a proportional amount of the summer 111 output as its signal which is dependent upon the potentiometer setting. The output signal from the potentiometer 116 is integrated with respect to time and inverted by the intem 'grator 118 and is presented on the output of the integraftor 118. The signal from the output of the integrator 118 is inverted through the inverter 124 and is presented as one of the inputs to the summer 111. From the analysis of the following relationships, it can be seen that the time constant T1 is produced. It is desirable to find the integrator output voltage from the module 106 in terms of the input voltage. It is also desirable to find the sum of the output voltage and the feedback voltage to the summer in terms of the input voltage. If Krepresents the potentiometer setting and T represents the time constant, then Moreover, if a, is equal to the integrator output voltage and ein is equal to the input voltage, it can be proved that:

a.- 1 i ein* 1+ Ts In order to determine the sum of the summer output voltage and the integrator output voltage in terms of the input voltage, it is only necessary to nd the summer output voltage in terms of the input voltage and add the same to the output voltage in terms of the input Voltage. Permitting es to represent the summer output voltage, it can be proved by the analysis of the above circuit that:

ein- Ts-i' 1 .Adding each of the above output voltage relationships, it can be seen that the s um of the summer output voltage and integrator output voltage in terms of the input voltage is equal to:

ein

and

eo1=integrator output voltage of module 106 eozzintegrator output voltage of module 107 eo3=integrator output voltage of module 108 e04=integrator output voltage of module 109 eo=integrator output voltage of module 110 and eim=input voltage from pulse generator to module 106 em2=input voltage from integrator of module 106 to summer of module 107 em3=input voltage from integrator of module 107 to summer of module 108 em4=input voltage from integrator of module 108 to summer of module 109 em5=input voltage from integrator of module 109 to summer of module 110 and T2=time constant of module 107 T3=time constant of module 108 T4=time constant of module 109 T5=time constant of module 110 it can be seen that:

and

; etc.

Thus, it can be seen In similar manner, the additional model sets can be written for the remaining terms in the model equation It can thus be seen that elm ein

produced by the module 109 and ein OSCILLATRY TRANSIENTS GENERATOR The orthogonal model M as hereinabove described is only capable of simulating a system with real roots in the denominator of its characteristic equation. In some processes, imaginary roots exist in the denominator of this same characteristic equation and this is exhibited by oscillatory transients. In order to accurately simulate processes of this latter type, it is necessary to provide a simulation of the oscillatory transient on the signal from the model. The oscillatory transients generator T is connected in parallel with the model M and may be optionally interposed in the circuit by means of the switch 30. By reference to FIGURES 2 and 3c, it can be seen that the switch 30 is a three position switch, having a plus, minus and off position. The transients generator is designed to produce a sinusoidal output of selected frequency and damping. The transients generator T is also designed to provide a variable phase shift of up to The switch 30 will provide a phase shift of 180 and coupled with the 90 phase shift can provide a complete eiective phase shift of 360. It is known that the solution of the following second order diierential equation is an oscillatory variance in the variable x.

where wn is the undampened natural frequency and g is the damping ratio. If p is substituted for d/dt, the characteristic equation may be written as:

For the limiting case where =l, critical damping occurs and the response is XU)=C5(1+wnl)emle When ,=0, the system is described by a sinusoid Therefore, the equation can be written as x(t) :Co cos wht The oscillatory transients generator circuit as illustrated in FIGURE 3c is an analogue of the solution to the above second order differential equation.

The oscillatory transients generator T comprises an inverter 166, the input of which is connected directly to the output of the pulse generator 13. The output of the inverter 166 is connected directly to the switch 30 which is, in turn, connected to the input of a summing inverter 167. The inverter 166 in combination with the switch 30 is designed to provide the 180 phase shift of the output signal from the transients generator T. The output of the summing inverter 167 is connected to a frequency adjusting potentiometer 168 having a control dial mounted on the control panel 5. The movable arm of the potentiometer is connected to a summing integrator 169 which integrates the signal from the potentiometer 168. The output of the summing integrator 169 feeds a second potentiometer 170 which is mechanically connected to and operable with the potentiometer 168 in the manner as illustrated in FIGURE 3c. The potentiometer 170 also adjusts the frequency. In effect, therefore, the two potentiometers 168 and 170 operating in tandem provide frequency adjustment The output of the potentiometer 170 is, in turn, connected to a second integrator 171 and the output of the integrator 171 for feedback to one of the inputs of the summing inverter 167A decay control potentiometer 172 having a dial mounted on the control panel 5 is connected to the output of the summing integrator 169 and to an input thereof. The decay control potentiometer 172 provides values of the damping ratio from 0 to 1. If the decay control potentiometer 172 is set at a 0 position, continuous oscillation would exist and if it were set at a maximum position of l, critical damping would occur. A phase control potentiometer 173 has a pair of terminals, one of which is connected to the integrator 169 and the other of which is connected to the integrator 171. The potentiometer 173 has a control dial mounted on the control panel 5. The phase control potentiometer 173 is designed to combine the oscillatory output of the integrator 169 and the output of the integrator 171 which has been delayed 90. The movable arm of the phase control potentiometer 173 is connected to the input of an inverter 174. By shifting the movable arm of the potentiometer 173 through its entire span, it is possible to obtain a change in phase of 90. The output of the inverter 174 is connected to an amplitude control potentiometer 175 having a control dial mounted on the control panel 5, the opposite end of the potentiometer 175 being grounded. The movable arm of the potentiometer 175 is connected through an input resistor 175 to the input of the amplifier 144 in the summer 131. The amplitude control potentiometer 175 is designed to vary the total amplitude of the oscillatory signal from the oscillatory transients generator T. The inte-l grator 169 and the integrator 171 are provided with reset relay contacts 176, which are operable by a reset relay coil 176 for resetting of the oscillatory transients generator T after each compute signal. The relay coil 176 is connected to and operable by the mode control circuit in the manner as previously described.

ELECTRICAL AND PNEUMATIC RANGE SELECTOR By reference to FIGURES 2, 3d and 3e, it can be seen that the signal from the pulse generator 13 is transmitted through a summer 177 to the selector switch 27 where transmission may be optionally directed to either the electrical range selector 22 or the electrical-to-pneumatic transducer 23. The block diagram 0f FIGURE 2 provides a schematic illustration of the function of the combined electrical and pneumatic range selector, the circuitry of which is illustrated in FIGURE 3e. The circuit, however, is combined so that the range selector 22 and the converter 23.function as a unitary component system. In like manner, the output of the process P is directed to the range converter 32 and pneumatic-toelectric transducer 31 in the block diagram of FIGURE 2. Again, this is a functional illustration and these two components are combined in the electric and pneumatic range selector of FIGURE 3e. In essence, the two converters 23, 31 and the two range selectors 22, 32 are combined to form the electrical and pneumatic range selector. However, by reference to FIGURE 3e, it can be seen that the upper portion of the circuit provides a se lection of the desired signal to the process and the lower portion of the circuit provides a selection of the desired signal from the process.

The summer 177 comprises an operational amplifier 178 with an input resistor 179 and a feedback resistor 180 so that the summer 177 also serves as an inverter. Also connected to the input of the amplifier 178 is an input resistor 181, which is also connected to the movable element of a static process position potentiometer 182 having a control dial 183 `mounted on the control panel 5. One terminal of the potentiometer 182 is connected to a minus reference voltage from the power supply S and the opposite terminal of the potentiometer 182 is grounded in the manner as shown in FIGURE 3e. Connected to the output of the amplifier 178 is a conventional voltmeter 184 having a dial face 185 mounted on the control panel 5 and which is designed to show the operating level of the process P. The output of the amplifier 178 and the voltmeter 184 is, in turn, connected to the movable element of the switch 27. The static process position potentiometer 182 and the voltmeter 184 are designed to provide the same reference level input signal from the pulse generator 13 on which the process P normally operates.

The switch 27 is a two position switch having an electrical position and a pneumatic position. By reference to FIGURES l and 3e, when the switch 27 is shifted to the pneumatic position (lower position), the signal from the output of the summer 177 is transmitted to the electrical-pneumatic or E-P transducer 23. Interposed between the switch 27 and the transducer 23 is a pneumatic range selector switch 186 having a plurality of pneumatic input ranges. The switch 186 is designed to have the ranges which are commonly found in pneumatic control systems. In the present application, a two position pneumatic range selector switch has been adopted since the vast majority of pneumatic control systems operate on a 3-15 p.s.i.g. or a 6-30 p.s.i.g. range. The output of the transducer 23 is provided with the pneumatic fitting 9 for optional connection to the process P. In this connection, it should be understood that the transducer 23r;nay be provided with more than one setting for variable situations.

When the switch 27 is shifted to the electrical posi tion (-upper position), the switch 27 is connected-'t0 a voltage divider circuit consisting of fixed resistors 187, 188. Connected to the common terminal of the resistors 187, 188 is a multiple position, rotary, electric range selector switch 189 having a desired electrical range at each range position. The pneumatic range selector switch 186 and the electrical range selector switch 189 have Acontrol dials 190, 191, respectively which are mounted'on the control panel I5 in the lmanner as -illustrated in FIG- URE 1. By further reference thereto, it can be seen that the range selector switch 189 herein employed is provided with four positions, namely a l-5 milliamp position, a -50 milliamp position, a l-5 volt position and a l-9 volt position.

The movable element of the range selector switch 189 is connected to a current voltage converter-192 which includes a summer-inverter 193 formed by an operational amplifier 194 with an input resistor 195 and a feedback resistor 196. The voltage current converter 192 also includes a second inverter circuit 197 having an operational amplifier 198, an input resistor 199 and a feedback resistor 200. Connected to the output of the amplifier 198 is a resistor 201 which serves as an input resistor to the amplifier 194. Connected to the output of the amplifier 194 is a series resistor 202 and a second series resistor 203.

By reference to FIGURE 3e, it can be seen that the upper position of the switch 189 is connected directly to' the upper position of the switch 27. The remaining positions are connected in common to the voltage divider resistors 187, 188. Connected to the series resistor.v 202 is the movable element of a four position switch 204. The

two current positions of the switch 204 are connected to the input resistor 199 and the two voltage positions of the switch 204 are connected to the output of the amplifier 194. Also 'connected to one terminal of the -series, re sister 203 is the -movable element of a four position rot'a'ry switch 205 having only the lowermost contact point connected directly to the output of the amplifier 194. It can be seen that the switches 189, 204 and 205 are mechanically actuated in common or ganged so that they operate in unison. Furthermore, only the control dal'191 of the switch 189 is mounted on the control panel 5 for common actuation of each of the switches 189, 2.0 and 205-. By further reference to FIGURE 3e, it can be seen that the amplifier 194 and the resistors 195, 196 and 201 form a summer inverter. When the switch 204 is in either of the two lower positions; that is, the current positions, the resistor 202 forms a positive feedback path through the inverter circuit 197 and back to the inverter 193. If the load resistance in the process were of zero magnitude, there would be no positive feedbackv loop, and thus the current in the resistor 202 is equivalent to minus the input voltage to the amplifier .194 divided by Ithe value of the resistor 202. If the resistanceof the process were of large magnitude, then the positiveieedbackriath through the inverter 197 would approximatelyequal the negative feedback across the resistor 196-fapdthis wouldV cause the output voltage ofthe amplifer1-194 to increase until the same value of current was attainedinl-thel resistor 202 that was present whenthe load wasof vzero resistancer When the switches 189, 204, and 205 arerunitarily Switched to the lowermost position, the resistor.203;.is1gp1aqediin parallel with the resistor 202 thus causingnmorel current to flow fromrthe amplifier. 194.tov the proeesstilrfoa given input voltage. Thus, it canbe seehlthatl whenltl'le switch 189 and'the unitarily actu`ate'd-s'vtii't'ol'ies204,o 205 are shifted to either of the lowermost positions, an output current signal is provided independently of the process resistance and dependent only on the input voltage signal to the voltage divider consisting of resistors 187, 188. When the switch 204 is shifted to either of the two upper positions, the series resistors 202, 203 are effectively re-s moved from the circuit and the positive feedback loop is also removed permitting the inverter 193 to operate as a negative feedback inverter. Thus, the output voltage of the inverter 193 is independent of the process resistance and dependent only on its input voltage. The switch 189 merely serves to change the scale of the input voltage current converter 192 by tapping the divider circuit consisting of resistors 187, 188. This type of range selector switching circuit where output voltage and output current is independent of load impedance is more fully illustrated and described in copending application Ser. No. 509,101 filed Nov. 22, 1965.

Thus, it can be seen that the desired input pulse can be manufactured and transmitted to the process '-P. The transmisison of the pulse to the process P will create an output pulse at the selected point of measurement. It should be recognized that the rapid process simulator A is not necessarily connected to the process either electrically or pneumatically. In many cases, the process is provided with process instrumentation which vmay be either pneumatic or electrical or both and the rapid process simulator A can be connected to the process in strumentation. However, when reference is made to an operative connection between the rapid process simulator A and the process P in this application, it should be understod that the process P is, therefore, defined to yinclude the process instrumentation associated therewith as well as the physical process itself. As pointed out above, the rapid process simulator A offers utility with mechanical, electrical, biological, chemical systems, etc. In fact, it can be realized that the rapid process simulator A can be employed with any process as long as conventional conversion components are ernployed to convert the signal of the process to either pneumatic or electrical signals as described herein. For

example, if a chemical system is to be analyzed which has pneumatic instrumentation, the E-P transducer 23 and the P-E transducer 31 are connected to the process. On the Vother hand, if the process has electrical instru mentation, the connecting lines from the electrical and pneumatic range selector are directly connected to the process at the desired input and output points.

Assuming that the process P was pneumatic and the transducer 32 was connected thereto at the desired output signal point, a pneumatic signal from the process P would be converted in the P-E converter 31 to an electrical signal for transmission to the movable arm of a pneumatic range selector switch 206. The pneumatic range selector switch 206 is substantially identical to the pneumatic range selector switch 186 and is ganged therewith so that the switch 206 is mechanically actuated by the switch 186. Therefore, the switch 206 is notmounted on the control panel 5. The input signal from the transducer 31 is also transmitted to a pair of series connected input resistors 207, 208 of a scale converter summer 209. By reference to FIGURE 3e, it can be seen that theswitch 206 is'connected across the resistor 207 for shorting the samey'in a manner hereinafter described in detail. The electrical output from the transducer 31 will have twice the` magnitude on the 6-30 scale as it does on the 3-15 scale'.- Th'us when the resistor 207, which has equal resistanceA value to the resistor 206, is shorted, the gain of the summer 209 is double. The summer 209 includes an operational amplifier 210 having a feedback resistor 211;

H=1`he|mod`e1 M normally operates on a static voltage levelshav'ingaizero magnitude. The process P obviously does fnot operatelon a zero static level and in order to rem'ove"thefstaticposition or quiescent value from the process outputf "signal,y 'a I secondl static process' position 

